EHD effects are studied in high conductivity MBBA layers aligned homeotropically with respect to all the interfaces. Both freely suspended and bound films are examined under ac fields acting transversely to the line of sight. The orientational distortion originates as two periodic waves close to the electrodes : The pattern symmetry is determined by their relative phase. For freely suspended films, both inphase and 180 degrees out of phase waves occur; the domains are non-centrosymmetric in the former case, and centrosymmetric in the latter. For bound films, only the in phase waves occur; further, close to the frequency cut-off, two oppositely drifting wave trains appear along the electrodes.